HandsOn 16 - The Hele-Shaw Experiment with Carrageenan
II. Preparing Carrageenan
III. Observational Analysis
Carrageenan is available from chemical supply companies (e.g., Sigma). Here, we describe how to prepare carrageenan solutions of various concentrations and pH. You will need:
2. Fixing the pH of the carrageenan solution. We recommend practicing the following procedure on a small quantity of your solution first. Initially the carrageenan solution will have a pH of between 8 and 9. Prepare a dilute solution of HCl acid (e.g., 2 ml of HCl (36.5-38%) in 100 ml of distilled water). Add the diluted HCl dropwise to your carrageenan solution, and mix the solution. Measure the pH of your solution using a pH meter (directions below) or with pH paper. By repeating this process, prepare carrageenan solutions of pH 3 and pH 5.
3. To adjust the pH of "pure'' water, add 1 ml of HCl to 100 ml of distilled water then take its pH. Adjust the pH by adding distilled water.
Once you have the desired pH, add food coloring to the HCl solution. This will provide contrast between the HCl solution and the carrageenan when performing the Hele-Shaw experiment.
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